Semiconductor technology is being improved in terms of integration degree, reliability and response speeds, as semiconductor memory devices are required to be operated at high speeds with large storage capacities. There has been some research on conductive structures of semiconductor devices having metal components. For example, tungsten silicide (WSi2) has been used for metal patterns in gate electrodes or bit line electrodes of semiconductor devices to reduce the electrical resistance of the metal patterns.
Conductive structures of a semiconductor device may be formed on a substrate through various unit processes such as a deposition process, an etching process and/or a patterning process. For example, an oxide layer and a conductive layer may be formed on the substrate by the deposition process, and etched from the substrate with a mask pattern. A conductive structure such as a gate structure may then be formed on the substrate by the patterning process.
A cleaning process may be performed on the substrate with the conductive structures, so that contaminants such as particles and/or by-products generated are removed. A general cleaning process may be performed using a mixture, such as an ammonium peroxide mixture (APM) or a sulfuric peroxide mixture (SPM), as a cleaning solution. However, some of the conductive structures may react with the cleaning solution, and may thereby be damaged or consumed in the cleaning process.
For at least these reasons, a reoxidation process may be performed on the substrate with the conductive structures in order to remedy the damage to one or more sidewalls of the conductive structure and/or to the surface of the substrate caused by the chemical reaction with the cleaning solution, and to change corner portions or edge portions of the bottom of the conductive structure to be rounded and smooth. This reoxidation process allows the conductive structures to compensate for some of the portions damaged and/or consumed by the chemical reaction with the cleaning solution and expand to prevent bowing and/or protrusion defects on the conductive structures. Recently, a plasma-type reoxidation process has been used as an alternative to a conventional furnace-type reoxidation process. However, when the plasma-type reoxidation process is used, a bowing defect is formed on a sidewall of a gate electrode in a longitudinal direction as shown in FIG. 1A, because the tungsten silicide (WSi2) does not adequately expand in the plasma-type reoxidation process, and thus the consumed portion of the tungsten silicide (WSi2) is not adequately restored in the plasma-type reoxidation process.
When the amount of the cleaning solution is decreased in order to minimize the chemical reaction of the conductive structures with the cleaning solution, contaminants such as the particles and/or by-products are not sufficiently removed from the conductive structure and/or the substrate. When the gate electrode is formed on the substrate and contaminants still remain on the gate electrode, the residual contaminants have an adverse effect on the manufacturing yield and reliability of the semiconductor device.
Accordingly, an improved cleaning process is needed to sufficiently remove the contaminants from the conductive structure and/or the substrate that minimizes the consumption of the conductive structures and/or the substrate.